This invention relates generally to an axle driving apparatus and, more particularly, relates to an integrated hydrostatic transaxle having an improved casing design.
Conventional hydrostatic transaxles are well known in the art. Examples of such transaxles and their operation may be seen in U.S. Pat. No. 5,330,394 to Hauser et al. The '394 patent is directed to a "Rider Transaxle Having Improved Hydrostatic Transmission" which patent is incorporated herein by reference in its entirety. These axle driving apparatuses are mainly used in small-sized vehicles, such as a mower tractor or the like. In their construction, the casing of the axle driving apparatus is typically formed by joining two main casing halves with each other, the junction surface therebetween commonly being referred to as the "split line".
Prior art casing designs are known to have several disadvantages. An example of one such disadvantage is fluid leakage. In particular, it has been noticed that when a shaft associated with the hydrostatic transmission or axle driving mechanism extends from the casing while being disposed on a spit line there is a tendency for hydraulic fluid and/or lubricating fluid to leak from the casing. This problem is typically caused as the half-rounds which support the shaft seals have a tendency to be misaligned when the casing halves are joined. Furthermore, as the known prior art designs require multiple casing sections to hold and maintain both the hydrostatic transmission and the axle driving mechanism, it is seen that there exists an increased cost in construction and increased weight owing to the required strength of the materials which are used therefor. In addition, it has also been seen that the use of multiple casing sections diminishes the structural integrity of the overall device.
As a result of these disadvantages, it is an object of the present invention to provide an improved axle driving apparatus casing which eliminates the problem associated with leakage caused by half-round misalignment. It is also an object of the present invention to provide an improved casing in which assembly of the component parts thereinto is simplified. It is yet another object of the present invention to provide a casing having improved structural integrity. It is still a further object of the present invention to provide an improved casing with reduced manufacturing cost and weight.